1. Field of the Invention
The invention is relative to a series for gear motors with differing theoretically outgoing or delivered torque and to a method of manufacturing the individual gear motors of the series.
2. Description of the Related Art
Hydraulic motors in the form of gear motors that convert the energy impressed on a current of liquid into a rotary movement with a certain torque and in which at least two gears meshing with each other and running with a narrow slot in a housing are used as displacing elements are known. As regards the type of displacing elements, two types are distinguished: gear motors with external gearing or toothing, and gear motors with internal gearing. See also in this connection Dubbel: Pocketbook for Machine Construction, 18th edition, H4 to H5.
The main characteristics of hydraulic motors are the theoretically outgoing final torque and the output speed range. However, the geometric displacement volume, absorption volume, and the nominal pressure of hydraulic motors also play a significant part in the selection of individual hydraulic motors. Due to the very different areas of application and requirements of use resulting therefrom, hydraulic motors are offered for different theoretically outgoing or delivered torques. They are offered as a rule, in series, in which the individual hydraulic motors of a series preferably have the same design but can differ significantly from each other in their characteristic values and dimensions and a corresponding increase in theoretically outgoing torque due to a change in the geometric displacement volume, e.g., an increase in absorption volume is associated with an enlargement of the construction size. An influencing of the displacement volume can be carried out in analogy with the influencing of the output volume, equivalent to the displacement volume, in pumps as in W. Gutbrod: xe2x80x9cThe Output Current of External and Internal Gear Pumps and Its Nonuniformityxe2x80x9d, German journal: Olhydraulik und Pneumatic 18 (1975) No. 2, pp. 97-104 and others by reducing or enlarging the tip circle of one of the two displacing elements. The enlargement of the possible theoretical geometrical displacement volume takes place thereby, e.g., in rather large intervals in groups and the essential distinguishing feature between the groups resides in the different radial dimensions of the displacing elements and axial interval of the gears. Within the group an elevation of the possible output volume takes place in smaller steps by enlarging the gearing width, that is, the extension of the gearing in axial direction. This has the result that the individual motors in drive [train] lines are not freely exchangeable as a rule if the requirements of use are changed since the latter differ sharply as regards the required construction space and similarities between the individual types can hardly be determined.
The invention therefore has the basic problem of creating a series for gear motors for differing theoretically outgoing lam torques and therewith different geometric displacement volumes that are suitable for different requirements of use in which series the individual motors have as many constructive features in common as possible and differ solely by slight modifications from each other. The hydraulic motors themselves are to be kept as small as possible as regards the required construction space and there should be the possibility of replacement with a hydraulic motor with a greater or lesser geometric displacement volume in hydrostatic systems without the entire drive chain having to be replaced or modified. In particular, modifications by altering the speed of the drive chain should be avoided.
A series of gear motors for differing theoretically outgoing torques and therewith differing geometric displacement volumes comprises at least two gear motors. Each gear motor comprises at least two gears meshing with one another as displacing elements. The invention provides that each gear motor in the series has the following construction features that are essentially identical as regards the dimension: Axial interval a between the geometric axes of the two gears meshing with one another and of the theoretical axes of rotation of the two gears meshing with one another; and gearing width, that is, extension of the gearing in an axial direction.
That is, there is no difference as regards the axial interval and the gearing width between the individual gear motors.
The differing theoretically outgoing torques and therewith different geometric displacement volumes are adjusted in accordance with the invention in gear motors of a series with the same axial interval between the individual displacing elements and a constant gearing width over the cog height. It is sufficient thereby if at least one of the two gears meshing with one another is changed as regards its tip circle diameter from one motor to the next motor in the series; however, in designs with only two gears meshing with one another it is preferable if the tip circle diameters of both gears are appropriately changed. This is preferably achieved by using a high gearing.
The inventor realized that relatively high output volumes can be achieved when using so-called high gearings since the sensitivity of the displacement volume over the tip circle diameter or the tip circle radius is significantly higher than in the case of normal gearings. Even slight changes in the tip circle are sufficient to achieve a corresponding increase of the output volume. The volumetric increase in radial direction of the individual gear motor in the direction of the geometric axes of the displacing elements, or of the axes of symmetry of the displacing elements is relatively slight. This statement also applies in an analogous manner to a diminution of the tip circle diameter or tip circle radius of an individual displacing element. The axial construction length remains constant for all gear motors of the series. A change of the construction unit size takes place only in radial direction during which only a lesser increase in volume for the entire gear motor construction unit is realized on account of the high sensitivity of displacement volume over the tip circle radius. The uniform axial construction length of the gear motor construction unit makes it possible to replace the gear motor arranged in a drive chain in accordance with the requirements of use on the theoretically outgoing torque and therewith displacement volume with another gear motor of this series that is designed for greater or lesser output volumes without the entire drive chain having to be replaced or readapted to the hydraulic motor to be used.
In an especially preferred embodiment of the gear motor series a constant transverse pitch p is assigned to the particular displacing elements, that is, gears of the individual hydraulic motors in the series, in the case of an axial interval that can be predefined and is constant for all hydraulic motors in the series, that is, the modulus as dimensional factor of the gearing is also constant for all gear motors so that there is the possibility of developing the displacing elements for the individual gear motors with differing output volumes from a motor arrangement with a unified basic displacing element as described, in which the basic gearing is designed for a maximum theoretical displacement volume of at least one of the two displacing elements as a high gearing and for lesser or minimal displacement volume the gearing or the individual gearing elements are reduced in size by removing metal or, in particular, milled down correspondingly to a smaller tip circle diameter. This procedure makes it possible to create a series for gear motors with different displacement volumes which are especially compact and very standardized as regards the individual elements used. The high degree of standardization results in a diminution of the manufacturing cost, which for its part is reflected in the total cost.
The design of the basic construction unit for the maximum theoretical displacement volume and therewith maximum theoretically outgoing torque as regards the individual gears meshing with each other takes place in accordance with the fundamentals for interpreting the geometry of gear pairs. This applies to the general instance that influence is exerted only on the cog height, regardless of the form, and to the especially advantageous embodiment in which, starting from a displacing element designed for maximum displacement volume, lesser displacement volumes can be realized by shortening the cog height, that is, removing material.
The solution of the invention can be used in gear motors with external gearing, and internal gearing. It is immaterial thereby whether the gear motors are single-stage or multistage gear motors.
In gear motors with externally cogged displacing elements, both displacing elements are preferably designed and constructed to be similar in their size and gearing geometry, whereas in the case of dual-stage or multistage gear motors, displacing elements with a differing design as regards geometry and dimensions are used.
The gearing itself is designed as an involute gearing. It should always be taken into consideration thereby that even upon a change of the tip circle diameters between the individual displacement elements of the individual motors of the series a seal is realized between the chamber for the output of displaced operating fluid and the pressure chamber as a result of the contacting of the flanks in order to assure the full functionality of the gear motor.
The solution in accordance with the invention is explained in the following, with reference made to the figures.